Add OCPP control for the Anker Solix EV charger (Own/Proxy CSMS)

The Anker Solix connector was read-only (cloud monitoring only). Add an
OCPP 1.6J control path with a per-user, cascading control mode:

  - off   monitoring only (default, unchanged behavior)
  - own   DriverVault is the charger's Central System (full control)
  - proxy DriverVault relays to Anker's cloud and injects commands

New internal/ocpp subsystem (stdlib-only, hand-rolled RFC 6455): a CSMS
with session management, inbound dispatch, and typed control commands
(RemoteStart/Stop, SetChargingProfile current limit, ChangeAvailability,
Reset, UnlockConnector, TriggerMessage, Get/ChangeConfiguration). Own- and
proxy-mode paths are verified end-to-end against a simulated charge point.

The charger connects to /ocpp/{serial}, authenticated with OCPP Basic auth
(serial + a per-charger control token) resolved to the owning user via an
in-memory token index. Control REST endpoints mirror the monitoring ones and
reuse the same cascade gate plus a live-session check. controlMode is a new
cascade field (global -> org -> user) advertised as a select on the plugin.

Frontend: control-mode select + provisioning card in Settings, and a real
Start/Stop/limit/reset control panel in Charging, gated on the active mode.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API Server/internal/plugins/builtin/ankersolix/ankersolix.go

@@ -143,6 +143,17 @@ func (p *Plugin) Descriptor() plugins.Descriptor {
 				Help: "Your Anker account password. Stored locally, sent only (encrypted) to Anker's login endpoint."},
 			{Key: "country", Label: "Country", Type: "text", Default: "DE",
 				Help: "ISO country code of your Anker account (e.g. DE, GB, US). Determines which Anker server the account lives on; a wrong value logs in but shows no devices."},
+			// controlMode selects the OCPP control path. It does not affect this
+			// (read-only) cloud plugin — the CSMS that acts on it lives in the api
+			// package (internal/ocpp) — but it is advertised here so a superadmin can
+			// set/lock it at the global layer, and it cascades like the other fields.
+			{Key: "controlMode", Label: "Control mode", Type: "select", Default: "off",
+				Help: "How DriverVault controls the charger over OCPP. Off = monitoring only (default). Own CSMS = the charger connects directly to DriverVault. Proxy CSMS = DriverVault relays to Anker's cloud and can inject commands.",
+				Options: []plugins.SelectOption{
+					{Value: "off", Label: "Off (monitoring only)"},
+					{Value: "own", Label: "Own CSMS (full control)"},
+					{Value: "proxy", Label: "Proxy CSMS (relay + control)"},
+				}},
 		},
 	}
 }

API Server/internal/plugins/builtin/ankersolix/ankersolix_test.go

@@ -43,6 +43,29 @@ func TestDescriptor(t *testing.T) {
 	if !fields["password"].Secret {
 		t.Error("password field must be marked secret")
 	}
+
+	// controlMode is a select advertising the three OCPP control paths.
+	cm, ok := fields["controlMode"]
+	if !ok {
+		t.Fatal("controlMode config field should be present")
+	}
+	if cm.Type != "select" {
+		t.Errorf("controlMode type = %q, want select", cm.Type)
+	}
+	if cm.Default != "off" {
+		t.Errorf("controlMode default = %q, want off", cm.Default)
+	}
+	want := map[string]bool{"off": false, "own": false, "proxy": false}
+	for _, o := range cm.Options {
+		if _, known := want[o.Value]; known {
+			want[o.Value] = true
+		}
+	}
+	for v, seen := range want {
+		if !seen {
+			t.Errorf("controlMode is missing option %q", v)
+		}
+	}
 }
 
 func TestRegistered(t *testing.T) {